Hard coating, target for forming hard coating, and method for forming hard coating

ABSTRACT

The present invention attempts to provide a hard coating which has excellent hardness and lubricity. Such attempt has been completed by providing a hard coating comprising
 
(Al 1-a V a ) (C 1-X N X ) wherein
 
0.27≦ a ≦0.75, and
 
0.3≦ X ≦1,
 
wherein a and X independently represent an atomic ratio.

FIELD OF THE INVENTION

This invention relates to a hard coating used in cutting tools such aschip, drill, and end mill, forging dies, and jigs and tools such asblanking punch; a target used in forming such a coating; and a methodfor depositing a hard coating.

BACKGROUND OF THE INVENTION

Cutting tools have been provided with wear resistance by forming a hardcoating of TiN, TiCN, TiAlN, or the like on a substrate of high speedsteel, cemented carbide, cermet, and the like. In particular, TiAlN hasbeen the favorable choice in the case of the coating formed on a highspeed cutting tool or a hardened cutting tool of, for example, hardenedsteel. With the recent increase in the hardness of the material to becut by the cutting tool and increase in the cutting speed, developmentof a hard coating having an improved wear resistance is highly demanded.JP-A No. 2003-71610, for example, discloses that use of TiCrAlN insteadof the TiAlN increases proportion of the AlN having rock-salt structurein the coating, and the coating hardness is thereby improvedsimultaneously with oxidation resistance.

The hard coating comprising TiAlN or TiCrAlN, however, is insufficientin lubricity in spite of the improved oxidation resistance at the hightemperature. Accordingly, cutting tools having such hard coating formedthereon often suffered from sticking of a part of the work piece ontothe surface of the cutting tool during the cutting operation. Jigs andtools such as forging dye and blanking punch also suffered from undulyincreased frictional resistance at the contact surface, and theyoccasionally experienced baking of the processed material onto the jigor the tool during the forging and pressing.

SUMMARY OF THE INVENTION

The present invention has been completed in view of the situation asdescribed above, and an object of the present invention is to provide ahard coating which has excellent hardness and lubricity, as well asrelated technologies.

According to one aspect of the present invention, a hard coating isprovided which has overcome the situation as described above. This hardcoating is

(1) a hard coating comprising (Al_(1-a)V_(a)) (C_(1-X)N_(X)) wherein0.27≦a≦0.75, and0.3≦X≦1,wherein a and X independently represent an atomic ratio; or

(2) a hard coating comprising (Al_(1-a-b-c)V_(a)Si_(b)B_(c))(C_(1-X)N_(X)) wherein0.1≦a≦0.75,0<b+c≦0.20, and0.3≦X≦1,wherein a, b, c, and X independently represent an atomic ratio with theproviso that b and c are not simultaneously 0 while one of b and c maybe 0.

The hard coating may be a multilayer hard coating, and such multilayerhard coating may be broadly divided into the following two embodiments.The first embodiment of the multilayer hard coating is the one producedby repeatedly depositing a thin layer comprising a nitride or acarbonitride of at least one element selected from Al, V, Si, and B. Theperiodicity is not more than 80 nm and the average compositioncalculated by multiplying the composition and the thickness of eachlayer and dividing the sum of the products by the thickness of theentire layer satisfies the composition of the above (1) or (2). Thesecond embodiment of the multilayer hard coating is the one produced byrepeatedly depositing (a) a thin layer comprising a nitride or acarbonitride of TiAl and/or a thin layer comprising a nitride or acarbonitride of CrAl, and (b) a thin layer having the compositionsatisfying the hard coating as described above. The periodicity is notmore than 80 nm.

The hard coating (including the multilayer hard coating) preferably hasa NaCl-type crystal structure. The hard coating of the present inventionexhibits both excellent hardness and excellent lubricity.

The hard coating (including the multilayer hard coating) may be disposedone on another (hereinafter sometimes referred to as laminate hardcoating). In such a laminate hard coating, each hard coating isdifferent from its adjacent hard coating layers.

The hard coating (including the multilayer hard coating and the laminatehard coating) may have deposited on one or both of its surfaces (1) adifferent hard coating or (2) a metal layer or an alloy layer(hereinafter sometimes referred to as a composite hard coating).

(1) Examples of the different hard coating include a hard coatingcomprising a metal nitride, a metal carbonate, or a metal carbonitridehaving a NaCl-type crystal structure.

(2) Examples of the metal layer or the alloy layer include a layer of atleast one metal selected from elements of Groups 4A, 5A, and 6A in thePeriodic Table, Al, and Si, and alloys thereof.

The hard coatings (1) and (2) may further contain Mo and/or W, andnamely, these coatings may be

(3) a hard coating comprising (Al_(1-a-d-e)V_(a)Mo_(d)W_(e))(C_(1-X)N_(X)) wherein0.2≦a≦0.75,0<d+e≦0.3, and0.3≦X≦1,wherein a, d, e, and X independently represent an atomic ratio with theproviso that d and e are not simultaneously 0 while one of d and e maybe 0, or

(4) a hard coating comprising(Al_(1-a-b-c-d-e)V_(a)Si_(b)B_(c)Mo_(d)W_(e)) (C_(1-X)N_(X)) wherein0.2≦a≦0.75,0<b+c≦0.20,0<d+e≦0.3, and0.3≦X≦1,wherein a, b, c, d, e, and X independently represent an atomic ratiowith the proviso that b and c are not simultaneously 0 while one of band c may be 0, and d and e are not simultaneously 0 while one of d ande may be 0.

The hard coating containing Mo and/or W is particularly excellent inlubricity and durability when used in a cutting tool under the hightemperature conditions of 600° C. or higher.

The hard coatings (1) and (2) may further contain Zr and/or Hf, andnamely, these coatings may be

(5) a hard coating comprising (Al_(1-a-f-g)V_(a)Hf_(f)Zr_(g))(C_(1-X)N_(X)) wherein0.01≦a≦0.75,0<f+g≦0.5, and0.3≦X≦1,wherein a, f, g and X independently represent an atomic ratio with theproviso that f and g are not simultaneously 0 while one of f and g maybe 0, or

(6) a hard coating comprising(Al_(1-a-b-c-f-g)V_(a)Si_(b)B_(c)Hf_(f)Zr_(g)) (C_(1-X)N_(X)) wherein0.01≦a≦0.75,0<b+c≦0.20,0<f+g≦0.5, and0.3≦X≦1,wherein a, b, c, f, g, and X independently represent an atomic ratiowith the proviso that b and c are not simultaneously 0 while one of band c may be 0, and f and g are not simultaneously 0 while one of f andg may be 0.

The hard coating containing Zr and/or Hr is particularly excellent inhardness under the high temperature conditions of 600° C. or higher.

The hard coatings (3) to (6) may preferably exhibit NaCl-type crystalstructure.

Also preferred is a laminate hard coating comprising a layer comprisingthe hard coating of the above (1) or (2) (hereafter referred to as layerA), and a layer comprising a compound obtained by selecting at least oneof Mo and W and at least one of C and N (hereafter referred to as layerB). In this case, the thickness of the layer A and the layer B ispreferably such that: the thickness of layer B≦the thickness of layerA≦200 nm.

Also preferred is a laminate hard coating comprising a layer comprisinga hard coating of any one of the above (1) or (2) (hereafter referred toas layer A), and a layer comprising a compound obtained by selecting atleast one of Zr and Hf and at least one of C and N (hereafter referredto as layer C). In this case, the thickness of the layer A and the layerC is preferably such that: the thickness of layer C≦the thickness oflayer A≦200 nm.

According to another aspect of the present invention, a hard coatingdeposited by arc ion plating is provided. This coating is deposited in agas containing 30 to 100% by atom of N in relation to the sum of N and Cby using a target comprising (Al_(1-a)V_(a)) wherein 0.27≦a≦0.75 whereina represents an atomic ratio, or a target comprising(Al_(1-a-b-c)V_(a)Si_(b)B_(c)) wherein 0.1≦a≦0.75 and 0<b+c≦0.20 whereina, b, and c independently represent an atomic ratio with the provisothat b and c are not simultaneously 0 while one of b and c may be 0.

According to further aspect of the present invention, a target fordepositing a hard coating is provided. This target comprises any one ofthe following elements (i) to (iv):

-   (i) Al and V,-   (ii) Al, V, and Si,-   (iii) Al, V, and B, and-   (iv) Al, V, Si, and B,    and the target has a relative density of not less than 95%.

Also provided by the present invention is a target for depositing a hardcoating, comprising (Al_(1-a)V_(a)) wherein0.27≦a≦0.75,wherein a represents an atomic ratio, and a target for depositing a hardcoating, comprising (Al_(1-a-b-c)V_(a)Si_(b)B_(c)) wherein0.1≦a≦0.75, and0<b+c≦0.20,

wherein a, b, and c independently represent an atomic ratio with theproviso that b and c are not simultaneously 0 while one of b and c maybe 0.

The hard coating may be produced, for example, by evaporating a metal ina film-forming gas atmosphere for ionization and promotingplasmatization of the film-forming gas together with the ionization ofsaid metal for the deposition of the coating

More specifically, in arc ion plating in which the metal constitutingthe target is evaporated and ionized by arc discharge, parallel ordivergent lines of magnetic force that extend in a directionsubstantially perpendicular to the evaporation surface of the target areformed, and plasmatization of the film-forming gas is promoted near theobject piece by these lines of magnetic force for depositing thecoating.

In such stage, magnetic flux density at a surface of the object piece onwhich the hard coating is to be coated is not less than 10 gauss. Inaddition, a magnetic field is preferably formed between the target andthe object piece such that the angle formed between the lines ofmagnetic force and the normal line of said target evaporation surface isnot more than ±30°.

In the hard coating of the present invention, the Al of the Al nitrideor the Al carbonitride hard coating has been replaced with an adequateamount of V, and therefore, it has excellent hardness and lubricity. Acutting tool having such hard coating will have an elongated life, and ajig or a tool having such hard coating will experience less seizing.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described in detail basedon the following figures, wherein:

FIG. 1 is a schematic view of the production apparatus used in theproduction method of the present invention.

FIG. 2 is a schematic view showing the distribution of the lines ofmagnetic force formed near the object piece in the production method ofthe present invention.

FIG. 3 is a schematic view showing the distribution of the lines ofmagnetic force formed near the object piece in the production method ofthe present invention.

FIG. 4 is a schematic view showing the distribution of the lines ofmagnetic force formed in the conventional arc ion plating.

FIG. 5 is a schematic view of the production apparatus used in theproduction method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The inventors of the present invention have prepared various hardcoatings and evaluated these coatings for their crystal structure,hardness, surface frictional resistance, and durability when depositedon a cutting tool in order to find a coating which is better than TiAlNand TiAlCN hard coatings (hereinafter sometimes generally referred to asTiAl-based hard coatings). The inventors then found that a nitride and acarbonitride produced by combining V with Al instead of Ti (for example,VAlN and VAlCN which are hereinafter sometimes generally referred to asVAl-based hard coatings) exhibit excellent hardness and lubricity(surface frictional resistance). The present invention is based on sucha finding.

More specifically, when a VAl-based hard coating is produced byreplacing Ti of a TiAl-based hard coating with V, a V oxide (V₂O₅ etc.)is believed to be preferentially formed by the frictional heat generatedat the boundary between the object piece or the work piece and the hardcoating since V is relatively susceptible to oxidization, and since thisV oxide is relatively soft and has a relatively low melting point,frictional resistance of the hard coating at the such boundary believedto become reduced. In addition, in the case of a VAl-based hard coating,hardness increases with the increase in the Al proportion as long as theNaCl-type crystal structure (also referred to as rock-salt structure,cubic system, or the like) is maintained, and when the Al proportion isexcessively high, the NaCl-type crystal structure collapses to generatea hexagonal system (also referred to as ZnS type or the like) and thecoating becomes soft. In the case of a VAl-based hard coating, the cubicsystem is maintained over a wider range of Al concentration comparedwith the TiAl-based hard coating, and this realizes a marked improvementin the hardness of the coating. Consequently, the VAl-based hard coatingis simultaneously provided with the excellent hardness and the excellentlubricity.

Such VAl-based hard coating may be expressed as (Al_(1-a)V_(a))(C_(1-X)N_(X)) wherein “a” and “X” independently represent an atomicratio. The “a” is not less than 0.27. When the “a” is too small,proportion of the Al will be excessively high and the coating will takehexagonal structure to invite decrease in the hardness (increase of thecoefficient of friction). The “a” is preferably not less than 0.3, andin particular, not less than 0.35. The hardness and the lubricity areimproved with the increase in the value of the “a”. However, when thevalue of the “a” is too high, accumulation of the strain realized by theuse of the Al with the V is reduced, and this invites decrease of thehardness and increase of the coefficient of friction. Accordingly, the“a” is preferably not more than 0.75, preferably not more than 0.6, andmore preferably not more than 0.5.

While the “X” may be 1 (that is, the hard coating may be a nitride),lubricity of the coating increases with the decrease in the value of the“X” (that is, increase in the amount of C”). However, an excessively low“X” is likely to invite formation of unstable AlC compound. Accordingly,“X” is preferably not less than 0.3, preferably not less than 0.4, morepreferably 0.5, and most preferably not less than 0.6.

The VAl-based hard coating may also have Si and/or B incorporatedthereto. Such VAl-based hard coating having Si and/or B added may beexpressed as (Al_(1-a-b-c)V_(a)Si_(b)B_(c)) (C_(1-X)N_(X)). It is to benoted that (Al_(1-a-b-c)V_(a)Si_(b)B_(c)) (C_(1-X)N_(X)) includes notonly the compounds wherein B is forming a carbonitride, and(Al_(1-a-b-c)V_(a)Si_(b)B_(c)) (C_(1-X)N_(X)) generally designatescompounds including those wherein B is forming a boride with Al, V, andSi. In the formula, “a”, “b”, “c” and “X” independently represent anatomic ratio. Addition of Si and/or B results in the smaller size of thecrystal grains in the VAl-based hard coating, and this invitesimprovement of the hardness. The mechanism of the crystal grain sizereduction is not precisely found out. However, crystal grain growth isbelieved to be suppressed by the formation of Si—N bond and B—N bond inthe grain boundary. In the VAl hard coating having the Si and/or B addedthereto, the value of the “a” is not less than 0.1 (preferably not lessthan 0.27, more preferably not less than 0.3, and most preferably notless than 0.35), and not more than 0.75 (preferably not more than 0.6,and more preferably 0.5). The amount of the Si and/or the B added (b+c)is more than 0, preferably not less than 0.01, and more preferably notless than 0.05. It is to be noted that either one or both of Si and Bmay be added in the composition, and one of the “b” and “c” may be 0.However, addition of B is more favorable than addition of Si because itforms the B—N bond that imparts lubricity to the coating. Accordingly,when the improvement in the lubricity is desired, addition of both Siand B or addition of B is recommended. On the other hand, excessiveaddition of the Si and/or the B invites transition of the crystalstructure of the VAl-based hard coating to the hexagonal system, andthis may invite loss of hardness. Accordingly, the amount of the Siand/or the B added (b+c) is not more than 0.20, preferably not more than0.15, and more preferably not less than 0.10, and in such a case, lowerlimit of the sum of the “a” and the “b+c” is preferably not less than0.4, and in particular, not less than 0.5.

The hard coating of the present invention is not limited to the one asdescribed above having a homogeneous composition, and also included inthe hard coating of the present invention are those having a compositionequivalent to the VAl-based hard coating (including the VAl-based hardcoating having the Si or the B added, and this also applies in thefollowing), the hard coating also having Mo and/or W incorporatedthereto as will be described below, or the hard coating having Zr and/orHf incorporated thereto as will be described below as the entirecoating. For example, a coating produced by repeatedly depositingextremely thin layers at a periodicity of not more than about 80 nm(hereinafter referred to as a multilayer hard coating) is also withinthe scope of the hard coating of the present invention when the averagecomposition falls within the composition of the VAl-based hard coating(or the hard coating also having Mo and/or W or the Zr and/or Hfincorporated thereto as will be described below) since the each layerconstituting such coating would have lost the unique property due to theextreme thinness of the layer in the case of such multilayer hardcoating (hereinafter sometimes referred to as the first multilayer hardcoating) and the coating in its entirety exhibits the characteristics ofthe single layer coating. Such multilayer hard coating also has themerit that the coating can be produced by using a combination of knowntargets (such as AlN and AlVN) with no need to produce a unique targetmatching the composition of the coating. The term “average composition”means the composition represented by the proportion of the number ofatoms present in the laminate per unit area and this average compositionmay be calculated, for example, by the procedure as described below.With regard to a laminate comprising layers A comprising (V_(a)Si_(b))N(thickness, X nm) and layers B comprising (Al_(c)B_(d))N (thickness, Ynm), for example, lattice constant (α) and number of molecules (Z) perunit cell of the compound constituting the layer A and the layer B per10⁶ nm² are determined by X ray diffraction. Composition of each layer Aand layer B is calculated by AES or the like and the film thickness iscalculated by TEM or the like. The resulting values are used tocalculate number of V atoms per unit area (Vm) of the layer A by usingthe equation 10⁶X×Z×a/(α³)/(a+b) and number of Si atoms per unit area(Sim) by using the equation 10⁶X×Z×b/(α³)/(a+b) for the Si in the layerA. Similarly, number of Al and B atoms per unit area in the layer B[(Alm) and (Bm)] are determined. The thus obtained values of the numberof atoms are used to calculate the proportion of the number of atoms perunit area [in the case of V, (Vm/(Vm+Sim+Alm+Bm))] to determine theaverage composition.

Upper limit of the periodicity is preferably 50 nm, more preferably 30nm, and most preferably 15 nm. Homogeneity of the coating, the hardness,and the lubricity all improves with the decrease in the upper limit ofthe periodicity. No lower limit is set for the periodicity. However,distinction between the multilayer hard coating and the hard coatinghaving the homogeneous composition becomes difficult with the decreasein the periodicity, and the lower limit may be, set, for example, atabout 1 nm (and in particular, at about 3 nm). As long as theperiodicity is within such range, thickness of the constituent layer isnot particularly limited. The layer, however, may be in the range of,for example, not more than 50 nm, preferably not more than 30 nm, andmore preferably not more than 10 nm.

The layers of the multilayer VAl-based hard coating generally comprise anitride and a carbonitride [a nitride and a carbonitride may behereinafter together referred to as a (carbo)nitride] of at least oneelement selected from Al, V, Si and B. Examples of the preferable(carbo)nitrides include Al-based (carbo) nitrides such as Al (CN), AlSi(CN), AlB (CN), and AlSiB(CN), and the foregoing compounds in which (CN)in the compound is (N); Si (CN), and B(CN) The combination of the layersis not particularly limited and the combination may be, for example, anAl-containing (carbo)nitride such as an Al-based (carbo)nitride or anAlV-based (carbo)nitride with an Al-free (carbo)nitride such as aV-based (carbo)nitride, Si (CN), or B(CN) Exemplary combinations includeAl (CN)/V(CN), Al (CN)/VSi (CN), AlSi(CN)/V(CN), AlSi(CN)/VB(CN),AlB(CN)/V(CN), AlB(CN)/VSi(CN), AlSiB(CN)/V(CN), AlV(CN)/Si(CN),AlV(CN)/B(CN), AlVSi(CN)/B(CN), AlVB(CN)/Si(CN), and AlVSiB(CN)/AlV(CN),and in the above exemplary combinations, the (CN) moiety may be (N).

The multilayer hard coating may also be the one comprising at least onehard coating layer having same composition as the VAl-based hard coating(including the hard coating having the Si or the B added), or the hardcoating also having Mo and/or W incorporated thereto as will bedescribed below, or the hard coating having Zr and/or Hf incorporatedthereto as will be described below (including those having the Si or theB added); and the remaining layers having the composition which does notsignificantly impair the properties of such hard coating (the secondmultilayer hard coating). In the case of such second multilayer hardcoating, the properties of the overall coating is determined by theproperties of the hard coating, and therefore, it has excellent hardnessand lubricity, and such coating is also within the scope of the hardcoating of the present invention.

Examples of such remaining layers having the composition which does notsignificantly impair the properties of such hard coating include a layercomprising a nitride or a carbonitride of TiAl, and a layer comprising anitride or a carbonitride of CrAl. These layers exhibit excellentoxidation resistance, and when such layer is laminated with the hardcoating (a VAl-based hard coating or a VAl-based hard coating having theSi and/or the B added thereto), the resulting laminate hard coatingwould be provided with the improved oxidation resistance. As long assuch remaining layers and the hard coatings are laminated one onanother, the number of the remaining layers is not limited, and thelaminate hard coating may include one or more such remaining layer.

The upper limit and the lower limit of the periodicity and the upperlimit and the lower limit of each layer may be the same as the firstmultilayer hard coating.

The thickness of the hard coating (total thickness of the layers whenthe hard coating comprises a plurality of layers) is typically not lessthan 0.5 times (preferably not less than 0.8 times, and most preferablynot less than 1.0 times) that of the remaining layers, and not more than2.0 times (preferably not more than 1.5 times) that of the remaininglayers. The hard layer is less likely to be affected by the remaininglayers when the proportion of the hard coating is higher in relation tothe remaining layers. Upper limit of the thickness of the hard layer inrelation to the remaining layers is not particularly limited, and thehigher proportion merely means that such coating would be difficult todistinguish from the hard coating having a homogeneous composition. Theupper limit, however, may be about 10 times (and in particular, about 5times, and typically, about 2 times).

In the case of a VAl-based hard coating (including the one having Siand/or B added), a V oxide which is relatively low melting and soft ispreferentially formed as described above by the friction at the boundarybetween the work piece (or the piece being cut), and this is believed toimprove the hardness and the lubricity. The melting point of the Voxide, however, is around 600° C., and sliding under the temperaturecondition higher than that may lead to oxidation of the V component inthe coating and the resulting susceptibility to degradation of thecoating. In view of such situation, the inventors of the presentinvention paid attention to Mo and W which form oxides having a meltingpoint higher than that of the V oxide, and succeeded in forming oxideshaving a melting point higher than that of the V oxide [WO₂ (meltingpoint, 1500° C.), WO₃ (melting point, 1470° C.), MoO₂ (melting point,1100° C.), and MoO₃ (melting point, 795 to 801° C.)] by using Mo and Walong with the (AlV) and (AlVSiB) components. The inventors also foundthat Such hard coating (hereinafter referred to as a VAl-based hardcoating having Mo and/or W incorporated therein, or simply as a hardcoating also containing Mo and/or W, and this VAl-based hard coatinghaving Mo and/or W incorporated therein may additionally contain Siand/or B) is capable of suppressing the oxidation speed even under hightemperature conditions of 600° C. or more, and also capable of improvingthe wear resistance and suppress the coefficient of friction to a lowerlevel.

The coefficient of friction can be suppressed and the wear resistancecan be improved when the content of the Mo and/or the W (atomic ratio)(that is, the value of “d+e” when the compound is expressed as(Al_(1-a-d-e)V_(a)Mo_(d)W_(e)) (C_(1-X)N_(X)) or(Al_(1-a-b-c-d-e)V_(a)Si_(b)B_(c)Mo_(d)W_(e)) (C_(1-X)N_(X)) as in thecase of the VAl-based hard coating as described above) is typically morethan 0, preferably not less than 0.05, and more preferably not less than0.1. However, when these elements are incorporated at an excessivelyhigh content, crystal structure of the hard coating becomes moresusceptible to undergoing transition from the hard NaCl-type structureto the soft hexagonal-type structure detracting from the wearresistance. Accordingly, the content of these elements (the value of“d+e”) is desirably controlled to not more than 0.3 (and preferably notmore than 0.2).

By the way, the VN and the AlN (pure and stable cubic structure) in thehard coating have a lattice constant of 0.414 nm and 0.412 nm,respectively, while ZrN and HfN respectively have a lattice constant of0.456 nm and 0.452 nm, which are larger than those of VN and AlN.Accordingly, in a hard coating having formed therein a compound such asZrN and HfN having a lattice constant different from those of the VN andthe AlN (hereinafter referred to a VAl-based hard coating also having Zrand/or Hf incorporated therein, or simply as a hard coating alsocontaining Zr and/or Hf, and this VAl-based hard coating having Zrand/or Hf incorporated therein may additionally contain Si and/or B),hardness can be improved by promoting the hardening by lattice strain.

The hardness and the wear resistance can be improved when the content ofthe Zr and/or the Hf (atomic ratio) (that is, the value of “f+g” whenthe compound is expressed as (Al_(1-a-f-g)V_(a)Hf_(f)Zr_(g))(C_(1-X)N_(X)) or (Al_(1-a-b-c-f-g)V_(a)Si_(b)B_(c)Hf_(f)Zr_(g))(C_(1-x)N_(x))s in the case of the VAl-based hard coating as describedabove) is typically more than 0, preferably not less than 0.1, and morepreferably not less than 0.2. However, when these elements areincorporated at an excessively high content, crystal structure of thehard coating becomes more susceptible to undergoing transition to thehexagonal structure detracting from the wear resistance. Accordingly,these elements are desirably incorporated at a content of not more than0.5 (preferably not more than 0.4, and not more than 0.3).

In the hard coating also containing Mo and/or W or the hard coating alsocontaining Zr and/or Hf, the coating may have a content of the V, Si, B,C, and N (that is, the values “a”, “b+c” and “X” in the above chemicalformula) similar to the VAl-based hard coating (including the hardcoating having the Si or the B added) as described above. However, Mo,W, Hf, and Zr have the effect of improving the wear resistance asdescribed above, and therefore, the lower limit of the content of V (thevalue of “a”) may be lower than those of the VAl-based hard coating orthe VAl-based hard coating including the hard coating having the Si orthe B added. The lower limit for the content of V (the value of “a”) inthe hard coating also containing Mo and/or W may be 0.2 (preferably0.27, more preferably 0.3, and most preferably 0.35), and the lowerlimit for the content of V in the hard coating also containing Zr and/orHf may be 0.01 (preferably 0.2, more preferably 0.27, still morepreferably 0.3, and most preferably 0.35).

The Mo and/or the W, or the Zr and/or the Hf may be incorporated in thehard coating not only by producing a single layer hard coatingcontaining such elements in its interior, but also by producing alaminate hard coating comprising the VAl-based hard coating (includingthe hard coating having the Si or the B added, and hereinafter referredto as layer A) and a layer of a compound produced from at least one ofMo and W and at least one of C and N (hereinafter referred to as layerB), or a layer of a compound produced from at least one of Zr and Hf andat least one of C and N (hereinafter referred to as layer C).

Metals such as Mo and/or W, or Hf and/or Zr are insufficient in thehardness, and deposition of such metal in the form of simple substancewill invite loss of the wear resistance of the overall laminate hardfilm. Therefore, these metals should be used with C and/or N in the formof a carbonitride-based compound. However, even when the metals such asMo and/or W, or Hf and/or Zr are incorporated in the carbonitride-basedcompound, such compound is still inferior in the hardness compared withthe VAl-based hard coating (including the hard coating having the Si orthe B added), and therefore, the hardness and the wear resistance of theoverall hard coating will be insufficient if the layer of thecarbonitride-based compound of the Mo, W, Hf, or Zr is thicker than theVAl-based hard coating. Therefore, the layer B and the layer C arepreferably deposited so that they would be thinner than the layer A.Furthermore, the thickness of respective layer is preferably controlledto not more than 200 nm (preferably not more than 50 nm, and morepreferably not more than 20 nm) since the advantage of producing alaminate coating is lost when the thickness of each layer exceeds acertain level.

The hard coating of the present invention [the VAl-based hard coating(including the hard coating having the Si or the B added), the VAl-basedhard coating also coating Mo and/or W (including the hard coating havingthe Si or the B added), the VAl-based hard coating also coating Zrand/or Hf (including the hard coating having the Si or the B added), amultilayer hard coating, or the like] may have a mixed crystal structureincluding both the cubic and hexagonal structures as long as the coatingexhibits the hardness and the lubricity (coefficient of friction) ofsatisfactory level. The coating will exhibit an increased hardness withthe increase in the proportion of the cubic crystal structure.

Whether the crystal structure is NaCl-type or not may be determined by Xray diffraction. More specifically, peak strength of the (111), (200),and (220) surfaces of the cubic crystal and the peak strength of the(100), (102), (110) surfaces of the hexagonal crystal are measured, andthe proportion of the cubic crystal is calculated by the followingequation (1). The crystal structure of coating may be determined to beNaCl-type when the thus calculated proportion of the cubic crystal isnot less than 0.7, preferably not less than 0.8, and not less than 0.9.In the coating having a mixed crystal structure in which this proportionis less than 0.7, this proportion is preferably not less than 0.4, andin particular, not less than 0.5.

$\begin{matrix}\frac{{I\;{B(111)}} + {I\;{B(200)}} + {I\;{B(220)}}}{\begin{matrix}{{I\;{B(111)}} + {I\;{B(200)}} + {I\; B(220)} +} \\{{I\;{H(100)}} + {I\;{H(102)}} + {I\;{H(110)}}}\end{matrix}} & (1)\end{matrix}$wherein IB(111), IB(200), and IB(220) respectively represent peakstrength of the surfaces of the cubic crystal, and IH(100), IH(102), andIH(110) respectively represent peak strength of the surfaces of thehexagonal crystal.

The X ray diffractometry is conducted by θ-2θ method. The X raydiffractometry of the cubic crystal is conducted by using a CuKα source,and the peak strength is measured, at, for example, about 2θ=37.78° forthe (111) surface, at, for example, about 2θ=43.9° for the (200)surface, and at, for example, about 2θ=63.8° for the surface (220). TheX ray diffractometry of the hexagonal crystal is conducted by using aCuKα source, and the peak strength is measured at, for example, about2θ=32° to 33° for the (100) surface, at, for example, about 2θ=48° to50° for the (102) surface, and at, for example, about 2θ=57° to 58° forthe (110) surface.

The peak positions indicated above for the cubic and hexagonal crystalsare those in accordance with the JCPDS card. The peak position of eachsurface of the crystal, and in particular, the hexagonal crystal(ZnS-type crystal) is sometimes deviated from the value indicated inJCPDS card when Ti, V, Cr, Mo, Ta, W, or the like is included in thecrystal. In such a case, the target peak position may be determined byconsidering the relation with other peak positions or the relation withthe peaks of other compounds.

Another hard coating different from the hard coating as described above,a metal layer, or an alloy layer may be deposited on at least onesurface of the hard coating to thereby produce a composite hard coating.

The hard coating different from the hard coating as described above is,more accurately, a hard coating of a metal nitride, a metal carbide, ora metal carbonitride having a NaCl-type crystal structure, which may beselected depending on the intended use of the coating. Typical examplesinclude Cr-based hard coatings such as Cr (CN) and CrAl (CN), and thosewherein the (CN) moiety is (N) or (C); Ti-based hard coatings such asTi(CN), TiAl(CN), and TiSi(CN), and those wherein the (CN) moiety is (N)or (C); and TiCr-based hard coatings such as TiAlCr(CN) and thosewherein the (CN) moiety is (N) or (C).

The metal layer or the alloy layer is, more accurately, a layer of atleast one metal selected from elements of Groups 4A, 5A, and 6A in thePeriodic Table, Al, and Si, and alloys thereof, and since such layer hasa hardness lower than that of the hard coating of the present invention,formation of the hard coating on the metal layer or the alloy layerintervening the hard coating and the object piece (in particular, aniron-based substrate comprising, for example, a high speed tool steel(e.g. SKH51 or SKD) which exhibits a relatively low adhesion with thehard coating) improves adhesion between the hard coating and the objectpiece. The metal layer or the alloy layer is typically a layercomprising Cr, Ti, Nb or Ti—Al.

The hard coating (including the laminate hard coating and the compositehard coating) may be deposited to a thickness adequately selecteddepending on the intended use. The thickness, however, is preferably notless than 0.5 μm (preferably not less than 1 μm) and not more than 20 μm(preferably not more than 15 μm, and more preferably not more than 10μm).

Examples of the iron substrate on which the hard coating is depositedinclude those comprising a high speed tool steel (SKH51, SKD11, SKD61,etc.) and cemented carbide.

The hard coating may be formed by a method known in the art such asphysical vapor deposition (PVD) or chemical vapor deposition (CVD), andpreferably, by PVD such as sputtering, vacuum deposition, and ionplating in view of the adhesion and the like. Preferably, the hardcoating is desirably formed by vapor deposition such as such assputtering and ion plating (and in particular, arc ion plating.

More specifically, the VAl-based hard coating or the VAl-based hardcoating having the Si and/or the B added thereto may be produced byvapor deposition, and preferably, by arc ion plating in the presence ofa film forming gas using the following target (i) to (iv):

-   (i) Al and V,-   (ii) Al, V, and Si,-   (iii) Al, V, and B, and-   (iv) Al, V, Si, and B.

More specifically,

when a hard coating comprising (Al_(1-a)V_(a)) (C_(1-X)N_(X)) is to bedeposited, a target comprising (Al_(1-a)V_(a)) wherein 0.27≦a≦0.75(wherein a represents an atomic ratio) may be employed, and

when a hard coating comprising (Al_(1-a-b-c)V_(a)Si_(b)B_(c))(C_(1-X)N_(X)) is to be deposited, a target comprising(Al_(1-a-b-c)V_(a)Si_(b)B_(c)) wherein 0.1≦a≦0.75, and 0<b+c≦0.20(wherein a, b, and c independently represent an atomic ratio with theproviso that b and c are not simultaneously 0 while one of b and c maybe 0) may be employed.

The target used in producing the hard coating also having Mo and/or W orthe Zr and/or Hf incorporated thereto may be a target of the above (i)to (iv) further comprising the Mo and/or the W, or the Zr and/or the Hf.

The inventors of the present invention also investigated the propertiesof the target, and found that a target having a relatively low densityis likely to be associated with microspores, and the non-uniformevaporation of the target results in the formation of a non-uniform hardcoating, and the low density target experiences local and rapidconsumption at the void portion of the target during the deposition ofthe coating, and the fast wearing speed of the target results in thereduced target life. The inventors also found that the large portion ofthe void in the target results in the reduced target strength as well asgeneration of cracks and the like. This problem could be solved byincreasing the relative density of the target to the degree of not lessthan 95% (preferably not less than 98%). Use of such target also enablesstabilization of the discharge state in the evaporation or ionization ofthe alloy component constituting the target by the arc discharge,thereby enabling production of the good hard coating.

The relative density used is the value determined by the formula:[(Weight of 1 cm³ of the target employed)/(Density of a target havingpure composition (theoretical density))×100]. The theoretical densitycan be calculated by using the method known in the art.

The production method of the target is not particularly limited. Thetarget is produced, for example, by homogeneously mixing the startingmaterial (V powder and Al powder) having adequately adjusted componentratio and particle size in a V blender or the like to produce a powdermixture, and producing the target from the mixture by cold isostaticpressing (CIP), hot isostatic pressing (HIP), hot extrusion,ultra-high-pressure hot pressing, or the like.

The inventors of the present invention also investigated the apparatusfor depositing the hard coating by arc ion plating, and found that, inthe apparatus used in the conventional AIP, target 106 is placed betweenmagnet 109 generating the magnetic field and work piece W, andtherefore, lines of magnetic force 102 generated by the magnet 109 aresubstantially parallel to the target surface near the evaporationsurface of the target as schematically shown in FIG. 4, and the lines ofmagnetic force 102 are less likely to extend to the vicinity of the workpiece W. As a consequence, density of the plasma of the film forming gaswhich is high near the target decreases toward the work piece W. Theinventors found that the hard coating can be efficiently deposited whenthe lines of magnetic force are generated so that they extend almostperpendicular to the evaporation surface of the target, and a portion ofthe electrons e generated by the discharge will collide with the Nand/or the C of the gas to facilitate plasmatization of the N and/or theC. More specifically, when a magnet or a means for generating magneticfield (also referred in the present invention as magnetic fieldgenerating means) 8 or 9 such as an electromagnet equipped with a coiland a power source for the coil is placed between a target 6 and thework piece W as shown in FIGS. 2 and 3, the angle formed between thelines of magnetic force and the line normal to the evaporating surfaceof the target 6 will be not less than ±30° (and preferably not less than20°). Also, when the magnetic flux density is increased near the targetand near the object piece to the level higher than the conventional AIPapparatus, generation of AlN having a rock salt-type crystal structurewhich is in non-equilibrium state at standard temperature and standardpressure can be promoted to thereby improve the hardness of the coating.Furthermore, plasmatization of the materials formed by the evaporationof the target and plasmatization of N in the atmospheric can be promotedto facilitate formation of high energy particles from the plasmatized N,and the inventors believe that this facilitates formation of the AlNhaving the rock salt-type structure in the non-equilibrium state.

The position where the magnetic field generating means is located may beabove the target 6 and/or on the side of the evaporating surface S ofthe target 6 so that the target is surrounded or sandwiched by themagnetic field generating means as shown in FIG. 2, or the magneticfield generating means 9 may be placed between the evaporating surface Sof the target and the work piece W as shown in FIG. 3. Alternatively,the chamber may be used as an anode as shown in FIG. 2, or aspecial-purpose cylindrical anode surrounding the front half of theperiphery of the target may be provided.

The intensity of the magnetic field generated may be adjusted so thatthe magnetic flux density at the central portion of the surface of theobject piece on which the hard coating is to be formed would be not lessthan 10 gauss (and preferably not less than 30 gauss).

The film forming gas may be selected depending on the composition of thedesired hard coating, and typically, such that N in relation to thetotal of the N and C atoms would be not less than 0.3% (and preferablynot less than 0.4%, more preferably not less than 0.6%, and mostpreferably not less than 0.8%).

The temperature of the object piece during deposition of the hardcoating may be adequately selected depending on the type of the objectpiece. When the temperature is too low, residual stress of the hardcoating may be increased, and an excessive residual stress acting on thehard coating may adversely affect the adhesion of the hard coating withthe object piece. Accordingly, the temperature of the object piece isdesirably adjusted to not less than 300° C., and preferably not lessthan 400° C. While the residual stress will be reduced with the increasein the temperature of the object piece, an excessively high temperatureof the object piece will invite simultaneous decrease of the compressivestress, and this may adversely affect the effect of the coating inimproving the bending resistance of the object piece. Such hightemperature may also invite deformation of the object piece.Accordingly, the temperature of the object piece is desirably adjustedto not more than 800° C., and preferably not more than 700° C. When theobject piece is a substrate of an HSS (high speed tool steel) such asSKH51 or a hot-working tool steel such as SKD11 or SKD61, thetemperature of the substrate during the production is preferablymaintained so that it does not exceed tempering temperature of thesubstrate material to thereby maintain the mechanical properties of thesubstrate. While the tempering temperature may be selected depending onthe substrate material, the tempering temperature is generally in therange of 550 to 570° C. when SKH51 is used for the substrate, and 500 to530° C. when SKD11 is used for the substrate. In such a case, thetemperature at the production of the substrate is preferably selected tobe lower than such tempering temperature, and typically, at atemperature not exceeding 50° C. below the tempering temperature.

The hard coating can be efficiently formed when a negative potential isapplied to the object piece during the formation of the coating. Thebias voltage applied is preferably a negative voltage of not less than10 V, and in particular, not less than 30 V in absolute value since thehigher vias voltage results in the higher energy of the plasmatized filmforming gas and metal ions, and formation of a hard coating having acubic crystal structure is facilitated. However, increase in the biasvoltage is sometimes associated with an extreme decrease in thedeposition speed of the coating due to etching of the coating by theplasmatized film forming gas. Accordingly, the bias voltage ispreferably maintained at a negative voltage of not more than 200 V, andin particular, not more than 150 V in absolute value. When the Alcontent is relatively low, the lock in as described above will beeffective even when if the bias voltage were somewhat low, and a hardcoating having cubic crystal structure is likely be deposited.

When the hard coating is produced as a laminate comprising a pluralityof hard coatings, such laminate coating may be produced, for example, byusing an apparatus as shown in FIG. 5 provided with a plurality oftarget 6A and magnetic field generating means 8A and forming each layerby the procedure as described above.

EXAMPLES

The hard coatings obtained in the following Experimental Examples wereevaluated for their physical properties by the method as describedbelow.

[Composition of the Hard Coating]

The composition was determined by EPMA. In this procedure, it was alsoconfirmed that content of the impurity other than metal elements andnitrogen, content of the oxygen, and content of the carbon arerespectively not more than 5 at %.

[Conditions used in Analyzing the Crystal Structure]

The hard coating was evaluated for the crystal structure by X raydiffraction by θ-2θ method using X ray diffractometer manufactured byRigaku Electric. The X ray diffractometry of the cubic crystal wasconducted by using a CuKα source, and the peak strength was measured, atabout 2θ=37.78° for the (111) surface at about 2θ=43.9° for the (200)surface, and at about 2θ=63.8° for the surface (220). The X raydiffractometry of the hexagonal crystal was conducted by using a CuKαsource, and the peak strength was measured at about 2θ=32° to 33° forthe (100) surface, at about 2θ=48° to 50° for the (102) surface, and atabout 2θ=57° to 58° for the (110) surface. The resulting values wereused in the following equation (1):

$\begin{matrix}\frac{{I\;{B(111)}} + {I\;{B(200)}} + {I\;{B(220)}}}{\begin{matrix}{{I\;{B(111)}} + {I\;{B(200)}} + {I\; B(220)} +} \\{{I\;{H(100)}} + {I\;{H(102)}} + {I\;{H(110)}}}\end{matrix}} & (1)\end{matrix}$wherein IB(111), IB(200), and IB(220) respectively represent peakstrength of the surfaces of the cubic crystal, and IH(100), IH(102), andIH(110) respectively represent peak strength of the surfaces of thehexagonal crystal. When the calculated value (“The value of equation(1)” in Table 1) was not less than 0.8, the coating was determined tohave NaCl-type structure (indicated in Table 1 as “B”); when the valuewas 0, the coating was determined to have hexagonal structure (indicatedin Table 1 as “H”); and when the value was more than 0 and less than0.8, the coating was determined to have a mixed structure (indicated inTable 1 as “B+H”).[Measurement of the Hardness]

The hardness was measured by a micro Vickers hardness tester at a loadof 0.25 N and retention time of 15 seconds.

[Measurement of the Coefficient of Friction]

The hard coating of the present invention was used on the surface of atest disk for sliding test (made of SKD61; diameter, 55 mm; thickness, 5mm; mirror finished on one surface), and the coating was evaluated forits coefficient of friction under the following test conditions.

Conditions of the Sliding Test

Test method: ball on disk

Ball: SUJ2 (diameter, 9.54 mm); Hardness, HRC60

Vertical load: 5 N

Sliding speed: 1 m/s

Atmosphere temperature: 500° C. for Experimental Examples 1 to 4, and800° C. for Experimental Examples 5 to 8.

Sliding distance: 1000 m

[Observation of the Wear Width]

The hard coating of the present invention was deposited on an end millof a cemented carbide (diameter 10 mm; 2 teeth) and cut to thepredetermined cutting length under the following the followingconditions A (Experimental Examples 1 to 4) and the following conditionsB (Experimental Examples 5 to 8), and the tip of the end mill coveredwith the hard coating was observed under an optical microscope.

-   Conditions A    -   Work piece: SKD61 hardened steel (HRC50)    -   Cutting rate: 220 m/minute    -   Feed rate: 0.06 mm/tooth    -   Axial cutting depth: 4.5 mm    -   Radial cutting depth: 1 mm    -   Misc.: only down cut, dry cut, and air blow    -   Cutting length: 20 m-   Conditions B    -   Work piece: SKD11(HRC60)    -   Cutting rate: 150 m/minute    -   Feed rate: 0.04 mm/tooth    -   Axial cutting depth: 4.5 mm    -   Radial cutting depth: 0.2 mm    -   Misc.: only down cut, dry cut, and air blow    -   Cutting length: 50 m        [The Apparatus Used in Depositing the Hard Coating]

An AIP apparatus schematically shown in FIG. 1 was used in ExperimentalExamples 1, 2, and 4 to 6. In FIG. 1, 1 designates a chamber, 2designates an arc evaporation source, 3 designates a support, 4designates a bias source, 6 designates a target, 7 designates an arcsource, 8 designates a means for generating a magnetic field (magnet),11 designates a gas outlet, 12 designates a gas inlet, and W designatesan object piece.

An AIP apparatus schematically shown in FIG. 5 was used in ExperimentalExamples 3, 7, and 8 to deposit the hard coating. The AIP apparatus ofFIG. 5 is the AIP apparatus of FIG. 1 further comprising an arcevaporation source 2A, a bias power source 4A, a target 6A, an arc powersource 7A, and a magnetic field generating means (magnet) 8A.

[Types of the Object Piece]

Three types of the object pieces were used in the Experimental Examples.The pieces used were: [1] a chip made of a cemented carbide (used forthe determination of the crystal structure and the hardness), [2] an endmill made of a cemented carbide (diameter 10 mm; two teeth) (used forthe measurement of the wear width), and [3] a disk for sliding test(made from SKD61; 55 mm (diameter)×5 mm (thickness); one side has beenmirror finished; used for the measurement of the coefficient offriction).

Experimental Example 1

[Formation of Hard Coating]

The target 6 used was the one having the composition indicated in the“Compositional ratio (atomic ratio) of the target” of Table 1.

The chamber 1 was evacuated, and the object piece was heated to 500° C.by using a heater (not shown). A single or mixed gas having thecomposition of “Compositional ratio (atomic ratio) of the film forminggas” shown in Table 1 was supplied to the chamber 1 from the gas inlet12 until the pressure of the chamber 1 reached 2.66 Pa. A voltage of 20to 100 V was applied to the object piece by the bias power source 4 suchthat the object piece W was negative to the earth voltage. Arc dischargewas then started by the arc power source 7 to vaporize and ionize thetarget 6 for deposition of a hard coating of 3 μm on the surface of theobject piece W.

[Physical Properties of Hard Coating]

The resulting hard coatings were evaluated for their crystal structure,the value of equation (1), hardness, coefficient of friction, and wearwidth. The results are shown in Table 1.

TABLE 1 Compositional Compositional ratio (atomic ratio (atomic ratio)of the ratio) of film forming Coefficient of the target gas Crystalstructure Hardness friction Wear width A1 V C N [The value of equation(1)] (HV) (μ) (μm) Comparative Example  1 Ti_(0.4)Al_(0.6)N B[1] 28000.67 55.0  2 Cr_(0.4)Al_(0.6)N B[1] 2750 0.56 54.0  3 0.00 1.00 0.001.00 B[1] 2750 0.28 56.0  4 0.20 0.80 0.00 1.00 B[1] 2950 0.29 54.0  50.75 0.25 0.00 1.00 B + H[0.2] 2700 0.58 37.0  6 0.85 0.15 0.00 1.00H[0] 2200 0.62 60.0  7 1.00 0.00 0.00 1.00 H[0] 2200 0.65 *  8 0.63 0.370.80 0.20 B[1] 2800 0.28 56.0 Example  1 0.25 0.75 0.00 1.00 B[1] 31000.29 33.0  2 0.35 0.65 0.00 1.00 B[1] 3200 0.29 35.0  3 0.40 0.60 0.001.00 B[1] 3350 0.3 25.0  4 0.60 0.40 0.00 1.00 B[1] 3400 0.3 22.0  50.63 0.37 0.00 1.00 B[1] 3450 0.34 18.0  6 0.65 0.35 0.00 1.00 B[1] 34500.35 18.0  7 0.68 0.32 0.00 1.00 B[1] 3400 0.38 18.0  8 0.70 0.30 0.001.00 B[1] 3000 0.39 20.0  9 0.73 0.27 0.00 1.00 B[1] 3300 0.34 20.0 100.63 0.37 0.15 0.85 B[1] 3500 0.31 19.0 11 0.63 0.37 0.30 0.70 B[1] 34900.3 23.0 12 0.63 0.37 0.42 0.58 B[1] 3300 0.3 25.0 13 0.63 0.37 0.550.45 B[1] 3150 0.29 29.0 14 0.63 0.37 0.66 0.34 B[1] 2950 0.29 46.0*Became unusable at 50 m

The hard coatings of the present invention comprising Al, V, C, and N(Examples 1 to 14) all exhibited superior hardness, lower coefficient offriction, and narrower wear width compared with the conventionalcoatings comprising TiAlN (Comparative Example 1), CrAlN (ComparativeExample 2), and VN (Comparative Example 3). The coatings outside thescope of the present invention (Comparative Examples 4 to 8) had acrystal structure containing hexagonal structure, and these coatingswere inferior either in the hardness, the coefficient of friction, orthe wear width compared with the conventional hard coating (ComparativeExamples 1 to 3). The coatings deposited by using a film forming gascontaining C (Examples 10 to 14) exhibited inferior frictionalresistance and superior lubricity compared with the one prepared byusing a film forming gas containing no C (Example 5).

Experimental Example 2

[Formation of Hard Coating]

The experiment was conducted by repeating the procedure of ExperimentalExample 1 except that target 6 used was the one having the compositionof the “Compositional ratio (atomic ratio) of the target” shown in Table2.

[Physical Properties of Hard Coating]

The resulting hard coatings were evaluated for their crystal structure,the value of equation (1), hardness, coefficient of friction, and wearwidth. The results are shown in Table 2.

TABLE 2 Compositional ratio (atomic Compositional ratio) of Coeffi-ratio (atomic the film Crystal cient Wear ratio) of the target forminggas Crystal structure grain size Hardness of friction width A1 V Si B CN [The value of equation (1)] (nm) (HV) (μ) (μm) Comparative Example  1Ti_(0.4)Al_(0.6)N B[1] 30 2800 0.67 55.0  2 Cr_(0.4)Al_(0.6)N B[1] 352750 0.56 54.0  9 0.51 0.25 0.00 0.24 0.00 1.00 H[0] 4 2650 0.21 43.0 100.53 0.20 0.27 0.00 0.15 0.85 H[0] 3 2700 0.4 53.0 11 0.57 0.20 0.110.12 0.55 0.45 H[0] 3 2800 0.35 55.0 Example 15 0.60 0.40 0.00 0.00 0.100.90 B[1] 20 3300 0.3 22.0 16 0.59 0.40 0.00 0.01 1.00 0.00 B[1] 16 34500.28 18.0 17 0.57 0.40 0.00 0.03 0.00 1.00 B[1] 15 3500 0.28 18.0 180.55 0.40 0.00 0.05 0.00 1.00 B[1] 12 3500 0.26 17.0 19 0.59 0.34 0.000.07 0.00 1.00 B[1] 10 3450 0.25 17.0 20 0.55 0.30 0.00 0.15 0.00 1.00B + H[0.5] 5 3100 0.23 20.0 21 0.55 0.25 0.00 0.20 0.00 1.00 B + H[0.5]5 3000 0.22 24.0 22 0.59 0.40 0.01 0.00 0.00 1.00 B[1] 10 3000 0.3 23.023 0.58 0.40 0.02 0.00 0.00 1.00 B[1] 8 3300 0.32 22.0 24 0.63 0.35 0.020.00 0.00 1.00 B[1] 8 3350 0.31 21.0 25 0.63 0.32 0.05 0.00 0.00 1.00B[1] 6 3300 0.33 22.0 26 0.40 0.30 0.10 0.00 0.00 1.00 B[1] 5 3300 0.3222.0 27 0.59 0.30 0.11 0.00 0.00 1.00 B[1] 5 3250 0.33 25.0 28 0.55 0.300.15 0.00 0.00 1.00 B[1] 5 3200 0.33 26.0 29 0.54 0.28 0.18 0.00 0.001.00 B + H[0.4] 3 3000 0.35 34.0 30 0.55 0.25 0.20 0.00 0.00 1.00 B +H[0.4] 3 3000 0.36 36.0 31 0.60 0.35 0.03 0.02 0.30 0.70 B[1] 7 34500.29 19.0 32 0.52 0.40 0.03 0.05 0.42 0.58 B[1] 6 3300 0.31 23.0 33 0.730.15 0.05 0.07 0.00 1.00 B + H[0.5] 5 2950 0.4 39.0

The hard coatings of the present invention (Examples 15 to 33) allexhibited superior hardness, lower coefficient of friction, and narrowerwear width compared with the conventional coatings comprising TiAlN(Comparative Example 1) and CrAlN (Comparative Example 2). The hardcoating further comprising Si and B (Examples 16 to 33) exhibitedequivalent or superior properties compared with the hard coating of thepresent invention not containing the Si or the B (Example 15). However,the coatings outside the scope of the present invention (ComparativeExamples 9 to 11) contained ZnS structure in their crystal structure,and exhibited equivalent or inferior hardness and wear width comparedwith the conventional hard coatings (Comparative Examples 1 and 2).

Experimental Example 3

[Formation of Hard Coating]

The apparatus used was the one schematically shown in FIG. 5. The target2 used was the one produced to have the composition indicated in the“Compositional ratio (atomic ratio) of the target” for “Layer A (upperrow)” of Table 3, and the target 2A used was the having the compositionindicated in the “Compositional ratio (atomic ratio) of the target” for“Layer B (lower row)” of Table 3. The coatings of Examples 39 and 41were deposited without using the target 2.

-   Formation of the Hard Coatings of Examples 34 to 38 and 40:

The chamber 1 was evacuated, and the object piece W was heated to 500°C. by using a heater (not shown). A single or mixed gas having thecomposition of “Compositional ratio (atomic ratio) of the film forminggas” shown in Table 3 was supplied to the chamber 1 from the gas inlet12 until the pressure of the chamber 1 reached 2.66 Pa. Arc dischargewas then started by the arc power source 7 to thereby vaporize andionize the target 6, and a voltage of 20 to 100 V was applied to theobject piece by the bias power source 4 such that the object piece W wasnegative to the earth voltage to thereby deposit layer A having thethickness indicated in Table 3 on the surface of the object piece. Arcdischarge was again started this time by the arc power source 7A tovaporize and ionize the target 6A, and a voltage of 20 to 100 V wasapplied to the object piece W by the bias power source 4 such that theobject piece W was in negative to the earth voltage to thereby depositlayer B having the thickness indicated in Table 3 on the surface of theobject piece W having the layer A already deposited thereon. Theprocedure as described above was repeated for the number indicated in“Number of deposition” in Table 3 to produce a hard coating comprisingthe laminate.

-   Formation of the Hard Coatings of Examples 39 and 41:

An object piece having the hard coating of “Layer A” of Table 3 on itssurface was used, and the object piece W was heated to 500° C. by usinga heater (not shown). A single or mixed gas having the composition of“Compositional ratio (atomic ratio) of the film forming gas” shown inTable 3 was supplied to the chamber 1 from the gas inlet 12 until thepressure of the chamber 1 reached 2.66 Pa. Arc discharge was againstarted this time by the arc power source 7A to vaporize and ionize thetarget 6A, and a voltage of 20 to 100 V was applied to the object pieceW by the bias power source 4 such that the object piece W was innegative to the earth voltage to thereby deposit layer B having thethickness indicated in Table 3 on the surface of the object piece W.

[Evaluation of Hard Coating]

The resulting hard coatings were evaluated for their crystal structure,the value of equation (1), hardness, coefficient of friction, and wearwidth. The results are shown in Table 3.

TABLE 3 Average Compo- Layer A (upper row)/Layer B (lower compositionalsitional Crystal row) ratio of the targets used ratio (atomic structureCoeffi- Compositional ratio in the formation Total ratio) of the Numb-[The cient (atomic ratio) of the Thick- of layer A and layer thick- filmforming er of value of Hard- of Wear target ness B (atomic ratio) nessgas depo- equation ness friction width A1 V Si B (nm) A1 V Si B (nm) C Nsition (1)] (HV) (μ) (μm) Compar- ative Example  1 Ti_(0.4)Al_(0.6)N 1B[1] 2800 0.67 55.0  2 Cr_(0.4)Al_(0.6)N 1 B[1] 2750 0.56 54.0 Example34 0.00 1.00 0.00 0.00 4 0.40 0.60 0.00 0.00 10.0 0.00 1.00 300 B[1]3250 0.25 20.0 1.00 0.00 0.00 0.00 6 35 0.00 0.96 0.04 0.00 3.7 0.630.36 0.01 0.00 10.0 0.00 1.00 300 B[1] 3300 0.31 21.0 1.00 0.00 0.000.00 6.3 36 0.00 1.00 0.00 0.00 3.8 0.59 0.38 0.00 0.03 10.0 0.05 0.95300 B[1] 3400 0.21 20.0 0.95 0.00 0.00 0.05 6.2 37 0.00 1.00 0.00 0.0030 0.60 0.40 0.00 0.00 75.0 0.00 1.00 40 B[1] 2850 0.5 48.0 1.00 0.000.00 0.00 45 38 0.69 0.31 0.00 0.00 6 0.582 0.402 0.012 0.004 10.0 0.050.95 300 B[1] 3250 0.24 35.0 0.42 0.54 0.03 0.01 4 39 TiN 500 3000 1B[1] 3350 0.28 20.0 0.60 0.37 0.00 0.03 2500 0.05 0.95 40Ti_(0.4)Al_(0.6)N 5 12 0.03 0.97 250 B[1] 3100 0.32 29.0 0.55 0.40 0.050.00 7 41 V 200 3000 1 B[1] 3200 0.29 25.0 0.60 0.37 0.00 0.03 2800 0.050.95

The hard coatings of the present invention having a laminate structure(Examples 34 to 41) all exhibited superior hardness, lower coefficientof friction, and narrower wear width compared with the conventionalcoatings comprising TiAlN (Comparative Example 1) and CrAlN (ComparativeExample 2).

Experimental Example 4

V, Al, Si, and B powders (each having a particle size of not more than100 mesh) were mixed in V blender to the composition indicated in Table4. The resulting powder was produced into a target under the conditionsof sintering (in a reducing atmosphere and at a sintering temperature of550° C.), HIP (10,000 atm, 480° C.), and hot casting (after heattemperature, 450° C.), respectively. The target was placed in the AIPapparatus shown in FIG. 1, and a hard coating was deposited on a surfaceof the object piece W. The object piece W was observed for the dischargesituation, and the coating formed. The results are shown in Table 4. Thefilm forming gas used was 100% nitrogen for Examples 42 and 43, and amixed gas of nitrogen and methane (nitrogen:methane=80:20 (atomicratio)) for Examples 44 and 45.

TABLE 4 Compositional ratio Production Relative (atomic ratio) of thetarget method of the density of the Crystal structure Hardness Wearwidth A1 V Si B target target [The value of equation (1)] (HV) (μm)Comparative Example 14 0.60 0.35 0.03 0.02 Sintering 88 No film could beformed due to discharge concentration 15 0.50 0.50 0.00 0.00 Sintering92 No film could be formed due to discharge concentration Example 420.60 0.40 0.00 0.00 HIP 97 B[1] 3250 21.0 43 0.57 0.40 0.00 0.03 HIP 99B[1] 3100 28.0 44 0.59 0.34 0.00 0.07 Hot forging 100 B[1] 3300 21.0 450.50 0.50 0.00 0.00 Hot forging 99 B[1] 3100 27.5

Attempt to deposit a hard coating by using the target having a relativedensity of less than 95% (Comparative Examples 14 and 15) failed, andthe hard coating could be deposited when a target having a relativedensity of 95% or higher was used (Examples 42 to 45).

Experimental Example 5

[Formation of Hard Coating]

The experiment was conducted by repeating the procedure of ExperimentalExample 1 except that target 6 used was the one having the compositionof the “Compositional ratio (atomic ratio) of the target” shown in Table5.

[Physical Properties of Hard Coating]

The resulting hard coatings were evaluated for their crystal structure,the value of equation (1), hardness, coefficient of friction, and wearwidth. The results are shown in Table 5.

TABLE 5 Compo- sitional ratio (atomic ratio) of the film CrystalCompositional ratio forming structure Coefficient Wear (atomic ratio) ofthe target gas [The value of Hardness of friction width A1 V W Mo Si B CN equation (1)] (HV) (μ) (μm) Comparative Example  1 Ti_(0.4)Al_(0.6)NB[1] 2800 0.85 100.0  2 Cr_(0.4)Al_(0.6)N B[1] 2750 0.78 110.0 16 0.450.16 0.39 0.00 0.00 0.00 0.00 1.00 B + H[0.4] 2800 0.35 53.0 Example 460.63 0.37 0.00 0.00 0.00 0.00 0.00 1.00 B[1] 3450 0.55 65.0 47 0.60 0.370.03 0.00 0.00 0.00 0.00 1.00 B[1] 3450 0.5 50.0 48 0.55 0.37 0.08 0.000.00 0.00 0.00 1.00 B[1] 3550 0.45 45.0 49 0.50 0.35 0.15 0.00 0.00 0.000.00 1.00 B[1] 3550 0.4 41.0 50 0.50 0.27 0.23 0.00 0.00 0.00 0.00 1.00B[1] 3500 0.39 46.0 51 0.50 0.35 0.00 0.15 0.00 0.00 0.00 1.00 B[1] 35000.41 39.0 52 0.50 0.35 0.07 0.08 0.00 0.00 0.00 1.00 B[1] 3500 0.39 39.053 0.65 0.20 0.10 0.05 0.00 0.00 0.00 1.00 B[1] 3000 0.4 45.0 54 0.550.40 0.05 0.00 0.00 0.00 0.00 1.00 B[1] 3500 0.45 43.0 55 0.50 0.40 0.050.05 0.00 0.00 0.00 1.00 B[1] 3550 0.45 41.0 56 0.40 0.30 0.15 0.15 0.000.00 0.00 1.00 B[1] 3400 0.46 47.0 57 0.50 0.35 0.10 0.00 0.05 0.00 0.001.00 B[1] 3480 0.4 36.0 58 0.50 0.31 0.07 0.07 0.05 0.00 0.00 1.00 B[1]3550 0.4 41.0 59 0.50 0.31 0.07 0.07 0.00 0.05 0.00 1.00 B[1] 3580 0.3842.0

The hard coating of Examples 47 to 59 corresponds to the results of thehard coating of the present invention containing W and/or Mo, and alsoshown for comparison purpose are the hard coating of the presentinvention containing no W or Mo (Example 46) and the conventional hardcoatings (Comparative Examples 1 and 2). Under the sliding conditions at800° C., the hard coatings containing the Mo and/or the W (Examples 47to 59) were superior in all of the hardness, the coefficient offriction, and the wear width compared with the conventional hardcoatings. In particular, in the case of a hard coating containing the Vat content of 0.27 or higher (Examples 47 to 52 and 54 to 56), all ofthe hardness, the coefficient of friction, and the wear width could beimproved by incorporating the W and/or the Mo in the hard coatingcompared with the hard coating of Example 46. However, when the totalcontent of the W and the Mo is 0.39 or higher, decrease in the hardnessand increase in the wear width was found due to emergence of hexagonalstructure-type crystal structure. (Comparative Example 16).

Experimental Example 6

[Formation of Hard Coating]

The experiment was conducted by repeating the procedure of ExperimentalExample 1 except that target 6 used was the one having the compositionof the “Compositional ratio (atomic ratio) of the target” shown in Table6.

[Physical Properties of Hard Coating]

The resulting hard coatings were evaluated for their crystal structure,the value of equation (1), hardness, coefficient of friction, and wearwidth. The results are shown in Table 6.

TABLE 6 Compos- itional ratio (atomic ratio) of the film CrystalCompositional ratio forming structure Coefficient Wear (atomic ratio) ofthe target gas [The value of Hardness of friction width A1 V Zr Hf Si BC N equation (1)] (HV) (μ) (μm) Comparative Example  1 Ti_(0.4)Al_(0.6)NB[1] 2800 0.85 100.0  2 Cr_(0.4)Al_(0.6)N B[1] 2750 0.78 110.0 Example46 0.63 0.37 0.00 0.00 0.00 0.00 0.00 1.00 B[1] 3450 0.55 65.0 60 0.600.37 0.03 0.00 0.00 0.00 0.00 1.00 B[1] 3450 0.53 50.0 61 0.55 0.37 0.080.00 0.00 0.00 0.00 1.00 B[1] 3500 0.51 47.0 62 0.50 0.35 0.15 0.00 0.000.00 0.00 1.00 B[1] 3560 0.53 39.0 63 0.50 0.27 0.23 0.00 0.00 0.00 0.001.00 B[1] 3500 0.55 47.0 64 0.50 0.05 0.45 0.00 0.00 0.00 0.00 1.00 B +H[0.35] 3100 0.56 51.0 65 0.50 0.05 0.00 0.45 0.00 0.00 0.00 1.00 B +H[0.30] 3050 0.57 53.0 66 0.50 0.35 0.00 0.15 0.00 0.00 0.00 1.00 B[1]3550 0.54 38.0 67 0.50 0.35 0.07 0.08 0.00 0.00 0.00 1.00 B[1] 3520 0.5438.0 68 0.35 0.25 0.40 0.00 0.00 0.00 0.00 1.00 B[1] 3400 0.52 48.0 690.35 0.25 0.00 0.40 0.00 0.00 0.00 1.00 B[1] 3450 0.52 47.0 70 0.35 0.250.25 0.15 0.00 0.00 0.00 1.00 B[1] 3450 0.5 48.0 70 0.50 0.40 0.10 0.000.00 0.00 0.00 1.00 B[1] 3500 0.53 45.0 72 0.50 0.30 0.20 0.00 0.00 0.000.00 1.00 B[1] 3550 0.52 40.0 73 0.50 0.35 0.10 0.00 0.05 0.00 0.00 1.00B[1] 3480 0.55 37.0 74 0.50 0.31 0.07 0.07 0.05 0.00 0.00 1.00 B[1] 35700.52 39.0 75 0.50 0.31 0.07 0.07 0.00 0.05 0.00 1.00 B[1] 3580 0.48 41.0

The hard coating of Examples 60 to 75 corresponds to the results of thehard coating of the present invention containing Zr and/or Hf, and alsoshown for comparison purpose are the hard coating of the presentinvention containing no Zr or Hf (Example 46) and the conventional hardcoatings (Comparative Examples 1 and 2). Under the sliding conditions at800° C., the hard coatings of Examples 60 to 75 were superior in all ofthe hardness, the coefficient of friction, and the wear width comparedwith the conventional hard coatings. In the case of the hard coatings ofExamples 60 to 75, increase in the hardness and decrease in the wearwidth over those of the hard coating of Example 46 could be realizedwith no significant change in the coefficient of friction byincorporating the Zr or the Hf. However, when the total content of suchelements (Zr and Hf) was 0.45 or higher, decrease in the hardness andincrease in the wear width started to take place due to emergence ofhexagonal structure-type crystal structure (Examples 64 and 65). Whilethe hardness and the wear width will not be inferior to the conventionalhard coatings (Comparative Examples 1 and 2) when such decrease is likethose of Examples 64 and 65, further increase in the total content ofthe Zr and the Hf will invite a significant decrease in the hardness aswell as a significant increase in the wear width.

Experimental Example 7

[Formation of Hard Coating]

The apparatus used was the one schematically shown in FIG. 5. InExamples 77 to 87, the target 2 used was the one produced to have thecomposition indicated in the “Compositional ratio (atomic ratio) of thetarget” for “Layer A (upper row)” of Table 7, and the target 2A used wasthe one produced to have the composition indicated in the “Compositionalratio (atomic ratio) of the target” for “Layer B (lower row)” of Table7, and the hard coating was deposited by using these targets. Thecoating of Example 76 was deposited without using the target 2. Exceptfor these, the procedure of Experimental Example 3 was repeated.

[Evaluation of Hard Coating]

The resulting hard coatings were evaluated for their hardness,coefficient of friction, and wear width. The results are shown in Table7.

TABLE 7 Layer A (upper row)/Layer B (lower row) Film Compositional ratioTotal forming Coefficient Wear (atomic ratio) of the target Thicknessthickness gas Number of Hardness of friction width A1 V W Mo Si B (nm)(nm) C N deposition (HV) (μ) (μm) Comparative Example  1Ti_(0.4)Al_(0.6)N 3000 3000 0.0 1.0 1 2800 0.85 100.0  2Cr_(0.4)Al_(0.6)N 3000 3000 0.0 1.0 1 2750 0.78 110.0 Example 46 0.650.35 0.00 0.00 0.00 0.00 3000 3000 0.0 1.0 1 3450 0.55 65.0 76 0.63 0.320.00 0.00 0.05 0.00 3000 3000 0.0 1.0 1 3300 0.57 55.0 77 0.65 0.35 0.000.00 0.00 0.00 20 3000 0.0 1.0 143 3450 0.55 45.0 0.00 0.00 1.00 0.000.00 0.00 1 78 0.65 0.35 0.00 0.00 0.00 0.00 20 3000 0.0 1.0 130 35000.51 34.0 0.00 0.00 1.00 0.00 0.00 0.00 3 79 0.65 0.35 0.00 0.00 0.000.00 20 3000 0.0 1.0 103 3550 0.46 40.0 0.00 0.00 1.00 0.00 0.00 0.00 980 0.65 0.35 0.00 0.00 0.00 0.00 20 3000 0.0 1.0 86 3500 0.43 41.0 0.000.00 1.00 0.00 0.00 0.00 15 81 0.65 0.35 0.00 0.00 0.00 0.00 20 3000 0.01.0 55 3400 0.4 53.0 0.00 0.00 1.00 0.00 0.00 0.00 35 82 0.65 0.35 0.000.00 0.00 0.00 20 3000 0.5 0.5 136 3500 0.41 34.0 0.00 0.00 1.00 0.000.00 0.00 2 83 0.60 0.35 0.00 0.00 0.00 0.05 20 3000 0.0 1.0 136 35500.4 41.0 0.00 0.00 1.00 0.00 0.00 0.00 2 84 0.63 0.32 0.00 0.00 0.050.00 55 3000 0.0 1.0 50 3550 0.43 40.0 0.00 0.00 0.00 1.00 0.00 0.00 585 0.63 0.32 0.00 0.00 0.05 0.00 80 3000 0.0 1.0 35 3500 0.43 42.0 0.000.00 0.00 1.00 0.00 0.00 5 86 0.63 0.32 0.00 0.00 0.05 0.00 150 3000 0.01.0 19 3450 0.53 53.0 0.00 0.00 0.00 1.00 0.00 0.00 10 87 0.63 0.32 0.000.00 0.05 0.00 30 3000 0.0 1.0 94 3550 0.43 42.0 0.00 0.00 0.50 0.500.00 0.00 2

The laminate hard coatings of the present invention (Examples 77 to 87)all exhibited superior hardness, lower coefficient of friction, andnarrower wear width compared with the conventional hard coatings(Comparative Examples 1 and 2). Decrease in the coefficient of frictionand the wear width over those of the single layer hard coating (Example46) could also be realized by depositing a laminate hard coating(Experimental Examples 77 to 83). The results of the single layer hardcoating of Example 76 and the laminate hard coatings of Examples 84 to87 also indicate that the embodiment of the present invention is fullyeffective for the hard coating containing Si.

Experimental Example 8

[Formation of Hard Coating]

The apparatus used was the one schematically shown in FIG. 5. InExamples 88 to 98, the target 2 used was the one produced to have thecomposition indicated in the “Compositional ratio (atomic ratio) of thetarget” for “Layer A (upper row)” of Table 7, and the target 2A used wasthe one produced to have the composition indicated in the “Compositionalratio (atomic ratio) of the target” for “Layer B (lower row)” of Table7, and the hard coating was deposited by using these targets. Except forthese, the procedure of Experimental Example 3 was repeated.

[Evaluation of Hard Coating]

The resulting hard coatings were evaluated for their hardness,coefficient of friction, and wear width. The results are shown in Table8.

TABLE 8 Layer A (upper row)/Layer B (lower row) Film Compositional ratioTotal forming Coefficient Wear (atomic ratio) of the target Thicknessthickness gas Number of Hardness of friction width A1 V Zr Hf Si B (nm)(nm) C N deposition (HV) (μ) (μm) Comparative Example  1Ti_(0.4)Al_(0.6)N 3000 3000 0.0 1.0 1 2800 0.85 100.0  2Cr_(0.4)Al_(0.6)N 3000 3000 0.0 1.0 1 2750 0.78 110.0 Example 46 0.650.35 0.00 0.00 0.00 0.00 3000 3000 0.0 1.0 1 3450 0.55 65.0 76 0.63 0.320.00 0.00 0.05 0.00 3000 3000 0.0 1.0 1 3300 0.57 55.0 88 0.65 0.35 0.000.00 0.00 0.00 20 3000 0.0 1.0 143 3300 0.55 50.0 0.00 0.00 1.00 0.000.00 0.00 1 89 0.65 0.35 0.00 0.00 0.00 0.00 20 3000 0.0 1.0 130 35000.55 44.0 0.00 0.00 1.00 0.00 0.00 0.00 3 90 0.65 0.35 0.00 0.00 0.000.00 20 3000 0.0 1.0 103 3600 0.54 40.0 0.00 0.00 1.00 0.00 0.00 0.00 991 0.65 0.35 0.00 0.00 0.00 0.00 20 3000 0.0 1.0 86 3550 0.56 35.0 0.000.00 1.00 0.00 0.00 0.00 15 92 0.65 0.35 0.00 0.00 0.00 0.00 20 3000 0.01.0 55 3500 0.55 45.0 0.00 0.00 1.00 0.00 0.00 0.00 35 93 0.65 0.35 0.000.00 0.00 0.00 20 3000 0.5 0.5 136 3500 0.54 34.0 0.00 0.00 1.00 0.000.00 0.00 2 94 0.60 0.35 0.00 0.00 0.00 0.05 20 3000 0.0 1.0 136 36000.56 41.0 0.00 0.00 0.00 1.00 0.00 0.00 2 95 0.63 0.32 0.00 0.00 0.050.00 55 3000 0.0 1.0 50 3450 0.5 40.0 0.00 0.00 0.00 1.00 0.00 0.00 5 960.63 0.32 0.00 0.00 0.05 0.00 80 3000 0.0 1.0 35 3500 0.53 47.0 0.000.00 0.00 1.00 0.00 0.00 5 97 0.63 0.32 0.00 0.00 0.05 0.00 150 3000 0.01.0 19 3600 0.56 55.0 0.00 0.00 0.00 1.00 0.00 0.00 10 98 0.63 0.32 0.000.00 0.05 0.00 30 3000 0.0 1.0 94 3550 0.53 42.0 0.00 0.00 0.50 0.500.00 0.00 2

The laminate hard coatings of the present invention (Examples 88 to 98)all exhibited superior hardness, lower coefficient of friction, andnarrower wear width compared with the conventional hard coatings(Comparative Examples 1 and 2). In the case of laminate hard coatings(Experimental Examples 87 to 93), increase in the hardness and decreasein the wear width could be realized with the coefficient of frictionsubstantially maintained at the same level as the single layer hardcoating (Example 46). The embodiment of the present invention is alsofully effective for the hard coating containing Si (Examples 95 to 98).

The hard coating of the present invention has extremely superb hardnessand lubricity, and therefore, it can be used in cutting tools (chip,drill, end mill, etc.) and jig and tools (forging dye, blanking punch,etc.), and also, in various automobile sliding members.

The foregoing invention has been described in terms of preferredembodiments. However, those skilled, in the art will recognize that manyvariations of such embodiments exist. Such variations are intended to bewithin the scope of the present invention and the appended claims.

1. A hard coating consisting of (Al_(1-a)V_(a))(C_(1-X)N_(X)), wherein0.35≦a≦0.75;0.3≦X≦1; a and X independently represent an atomic ratio; and the hardcoating comprises a NaCl-type crystal structure.
 2. The hard coatingaccording to claim 1, wherein 0.35≦a≦0.6.
 3. The hard coating accordingto claim 1, wherein 0.35≦a≦0.5.
 4. The hard coating according to claim1, wherein 0.4≦X≦1.
 5. The hard coating according to claim 1, wherein0.5≦X≦1.
 6. The hard coating according to claim 1, wherein 0.6≦X≦1.
 7. Ahard coating consisting of (Al_(1-a-b-c)V_(a)Si_(b)B_(c))(C_(1-X)N_(X)),wherein0.35≦a≦0.75;0<b+c≦0.20;0.3≦X≦1; a, b, c, and X independently represent an atomic ratio with theproviso that b and c are not simultaneously 0 while one of b and c maybe 0; and the hard coating comprises a NaCl-type crystal structure. 8.The hard coating according to claim 7, wherein 0.35≦a≦0.6.
 9. The hardcoating according to claim 7, wherein 0.35≦a≦0.5.
 10. The hard coatingaccording to claim 7, wherein 0.01<b+c≦0.15.
 11. The hard coatingaccording to claim 7, wherein 0.05<b+c≦0.10.
 12. The hard coatingaccording to claim 7, wherein 0.4≦a+b+c.
 13. The hard coating accordingto claim 7, wherein 0.5≦a+b+c.
 14. The hard coating according to claim7, wherein 0.4≦X≦1.
 15. The hard coating according to claim 7, wherein0.5≦X≦1.
 16. The hard coating according to claim 7, wherein 0.6≦X≦1. 17.A hard coating consisting of(Al_(1-a-b-c-d-e)V_(a)Si_(b)B_(c)Mo_(d)W_(e))(C_(1-X)N_(X)), wherein0.2≦a≦0.75;0<b+c≦0.20;0<d+e≦0.30;0.3≦X≦1; a, b, c, d, e, and X independently represent an atomic ratiowith the proviso that b and c are not simultaneously 0 while one of band c may be 0, and d and e are not simultaneously 0 while one of d ande may be 0; and the hard coating comprises a crystal structure includingat least one of a cubic structure and a hexagonal structure.
 18. A hardcoating consisting of (Al_(1-a-f-g)V_(a)Hf_(f)Zr_(g))(C_(1-X)N_(X)),wherein0.35≦a≦0.75;0<f+g≦0.5; and0.3≦X≦1; a, f, g and X independently represent an atomic ratio with theproviso that f and g are not simultaneously 0 while one of f and g maybe 0; and the hard coating comprises a crystal structure including atleast one of a cubic structure and a hexagonal structure.
 19. A hardcoating consisting of(Al_(1-a-b-c-f-g)V_(a)Si_(b)B_(c)Hf_(f)Zr_(g))(C_(1-X)N_(X)), wherein0.01≦a≦0.75;0<b+c≦0.20;0<f+g≦0.5;0.3≦X≦1; a, b, c, f, g, and X independently represent an atomic ratiowith the proviso that b and c are not simultaneously 0 while one of band c may be 0, and f and g are not simultaneously 0 while one of f andg may be 0; and the hard coating comprises a crystal structure includingat least one of a cubic structure and a hexagonal structure.
 20. A hardcoating deposited by arc ion plating in a gas containing 30 to 100% byatom of N in relation to the sum of N and C by using a target comprising(Al_(1-a)V_(a)), wherein 0.35≦a≦0.75 and a represents an atomic ratio,or a target comprising (Al_(1-a-b-c)V_(a)Si_(b)B_(c)), wherein0.1≦a≦0.75; 0<b+c≦0.20; and a, b, and c independently represent anatomic ratio with the proviso that b and c are not simultaneously 0while one of b and c may be 0; wherein the hard coating comprises aNaCl-type crystal structure.